Increased magnetoresistance in an inverted orthogonal spin transfer layer stack

ABSTRACT

A magnetic device includes a pinned magnetic layer and a free magnetic layer including a first body-centered cubic material and having a variable magnetization vector that has a first stable state and a second stable state. The magnetic device also includes a first non-magnetic layer and a reference layer. The first non-magnetic layer spatially separates the pinned magnetic layer and the free magnetic layer and includes a second body-centered cubic material that interfaces with the first body-centered cubic material. The magnetic device includes a second non-magnetic layer spatially separating the free magnetic layer and the reference magnetic layer. A magnetic tunnel junction, located below the pinned magnetic layer, is formed by the free magnetic layer, the second non-magnetic layer, and the reference magnetic layer. Application of a current pulse through the magnetic device switches the variable magnetization vector.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/715,073, filed on Oct. 17, 2012, which isincorporated by reference herein in its entirety.

BACKGROUND

Orthogonal spin transfer magnetic random access devices (OST-MRAM™)incorporate a polarizer. The devices and layer stacks are discussed inU.S. Pat. No. 6,980,469, the entirety of which is incorporated byreference. Roughness within and near the magnetic tunnel junction of alayer stack impacts performance of the OST™ device. Increased roughnesscan negatively impact the breakdown of the magnetic tunnel junction. AnOST™ layer stack with the polarizer on the top of the stack can reducethe roughness of the magnetic tunnel junction, increase the devicemagnetoresistance, and improve the performance of OST™ memory devices.

SUMMARY

In general, one aspect of the subject matter described in thisspecification is embodied in a magnetic device that includes a pinnedmagnetic layer that has a first fixed magnetization vector with a firstfixed magnetization direction. The magnetic device also includes a freemagnetic layer including a first body-centered cubic material and havinga variable magnetization vector having at least a first stable state anda second stable state. The magnetic device also includes a firstnon-magnetic layer and a reference layer. The first non-magnetic layerspatially separates the pinned magnetic layer and the free magneticlayer and includes a second body-centered cubic material that interfaceswith the first body-centered cubic material. The reference magneticlayer has a second fixed magnetization vector with a second fixedmagnetization direction. The magnetic device also includes a secondnon-magnetic layer spatially separating the free magnetic layer and thereference magnetic layer. A magnetic tunnel junction is formed by thefree magnetic layer, the second non-magnetic layer, and the referencemagnetic layer. Application of a current pulse, having either positiveor negative polarity and a selected amplitude and duration, through themagnetic device switches the variable magnetization vector. The magnetictunnel junction is spatially located below the pinned magnetic layer.Other implementations of memory devices and memory systems are describedin greater detail below.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects,implementations, and features described above, further aspects,implementations, and features will become apparent by reference to thefollowing drawings and the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several implementations in accordance withthe disclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1 is an illustration of a magnetic device.

FIG. 2 is an illustration of a magnetic device with an inverted layerstack in accordance with an illustrative implementation.

FIG. 3 is an illustration of an inverted layer stack with the polarizer(FM1) at the top of the stack in accordance with an illustrativeimplementation.

FIG. 4 is an illustration of an inverted layer stack with a syntheticantiferromagnet polarizer in accordance with an illustrativeimplementation.

FIG. 5 is an illustration of an inverted layer stack with a pinnedsynthetic antiferromagnet polarizer in accordance with an illustrativeimplementation.

FIGS. 6A and 6C are transmission electron microscope cross sections of anon-inverted layer stack.

FIGS. 6B and 6D are transmission electron microscope cross sections ofan inverted layer stack in accordance with an illustrativeimplementation.

FIG. 7 is an illustration of an inverted magnetic tunnel junctionwithout a polarizer on top in accordance with an illustrativeimplementation.

FIG. 8 is an illustration of an inverted layer stack in accordance withan illustrative implementation.

FIG. 9 is an illustration of a fcc non-magnetic layer for use in aninverted layer stack in accordance with an illustrative implementation.

FIG. 10 is an illustration of a bcc non-magnetic layer inverted for usein an inverted stack in accordance with an illustrative implementation.

FIG. 11 is an illustration of a fcc and a bcc non-magnetic layer for usein an inverted layer stack in accordance with an illustrativeimplementation.

FIG. 12 is a graph of current in plane tunneling measurements of themagnetoresistance of two layer stacks in accordance with an illustrativeimplementation.

All numerical thicknesses illustrated in the figures are nanometers(nm). Reference is made to the accompanying drawings throughout thefollowing detailed description. In the drawings, similar symbolstypically identify similar components, unless context dictatesotherwise. The illustrative implementations described in the detaileddescription, drawings, and claims are not meant to be limiting. Otherimplementations may be utilized, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presented here.It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in thefigures, can be arranged, substituted, combined, and designed in a widevariety of different configurations, all of which are explicitlycontemplated and made part of this disclosure.

DETAILED DESCRIPTION

Structure of a Basic Magnetic Device

FIG. 1 shows a prior art multilayered, pillar-shaped magnetic devicecomprising a pinned magnetic layer FM1 with a fixed magnetizationdirection and a free magnetic layer FM2 with a free magnetizationdirection. m₁ is the magnetization vector of the pinned magnetic layerFM1, and m₂ is the magnetization vector of the free magnetic layer FM2.The pinned magnetic layer FM1 acts as a source of spin angular momentum.

The pinned magnetic layer FM1 and the free magnetic layer FM2 areseparated by a first non-magnetic layer N1 that spatially separates thetwo layers FM1 and FM2. N1 may be a non-magnetic metal (Cu, CuN, Cr, Ag,Au, Al, Ru, Ta, TaN, etc.) or a thin non-magnetic insulator such asAl₂O₃ or MgO. When N1 is a non-magnetic metal its thickness must be lessor approximately equal to the spin-diffusion length in the material atthe temperature of the device. This allows the electronspin-polarization to be substantially maintained as electrons traverseN1. In one implementation where Cu is used, the thickness of the layerbe less than or approximately equal to 0.5 to 50 nm for a deviceoperating at or near room temperature. When N1 is an insulating layer,its thickness must be such that electrons can traverse this layer byquantum mechanical tunneling and mainly preserve their direction ofspin-polarization in this process. In an implementation where N1 is MgOor Al₂O₃, the layer should be approximately equal to 0.3 to 4 nm inthickness. The thickness of the non-magnetic layer N1 should be suchthere is an absence of scattering of the electron spin-direction on ashort length scale, which is less than about the layer thickness. Thepillar-shaped magnetic device is typically sized in nanometers, e.g., itmay be less than approximately 200 nm laterally.

The free magnetic layer FM2 is essentially a magnetic thin film elementimbedded in a pillar-shaped magnetic device with two additionallayers—the pinned magnetic layer FM1 and the non-magnetic layer N1. Thelayer thicknesses are typically approximately 0.7 nm to 10 nm.

These pillar-shaped magnetic devices can be fabricated in a stackedsequence of layers by many different means, including physical vapordeposition (sputtering), thermal and electron-beam evaporation through asub-micron stencil mask. These magnetic devices can also be fabricatedin a stack sequence using sputtering, thermal and electron-beamevaporation to form a multilayered film followed by a subtractivenanofabrication process that removes materials to leave thepillar-shaped magnetic device on a substrate surface, such as that of asilicon of other semiconducting or insulating wafer. The semiconductingwafer may already include portions of the CMOS circuitry for reading andwriting the magnetic device. Annealing may be used when the layer stackincorporates a magnetic tunnel junction. Annealing can crystallize anMgO insulating barrier and enhance the junction magnetoresistance. Invarious implementations, a single annealing process is used. In oneimplementation, the stacks are annealed at a temperature of 300 C to 450C to thermally crystallize the MgO layer. The duration of the annealingis minutes (a rapid thermal anneal) to several hours, with higherannealing temperatures requiring shorter annealing times. The annealingis often done in a magnetic field of 1 Tesla or greater to set themagnetic state of the reference layer (FM3). The annealing provides apreferred direction of magnetic anisotropy and an enhanced uniaxialmagnetic anisotropy of the free layer (FM2).

Materials for the ferromagnetic layers include (but are not limited to)Fe, Co, Ni; alloys of these elements, such as Ni_(1-x)Fe_(x), and CoFe;alloys of these ferromagnetic metals with non-magnetic metals, such asB, Cu, V, Pd, and Pt at compositions in which the materials areferromagnetically ordered at room temperature; conducting materials;conducting magnetic oxides such as CrO₂ and Fe₃O₄; and fullyspin-polarized materials such as the Heusler alloy NiMnSb. For thenonmagnetic layers, materials include (but are not limited to) Cu, CuN,Cr, Ag, Au, Al, Ru, Ta, and TaN.

An electric current source is connected to the pinned magnetic layer FM1and the free magnetic layer FM2 so that an electric current, I, cantraverse the pillar device. In another implementation, an electricalcontact is made to the top and bottom of a pillar that incorporates thelayer stack.

FIG. 2 is an illustration of an inverted layer stack 200 in accordancewith an illustrative implementation of the invention. In thisimplementation, the inverted layer stack 200 contains a pinned layerFM1. The pinned layer FM1 can be magnetized perpendicular to the planeof the layer, and is represented by m₁ in FIG. 2. The pinned layer FM1can be inverted with respect to the free magnetic layer FM2. In otherwords, the pinned layer FM1 is formed after the free magnetic layer FM2and the reference layer FM3. A non-magnetic layer N1 separates thepinned layer FM1 and the free magnetic layer FM2. The free magneticlayer FM2 can form a magnetic tunnel junction with another non-magneticlayer N2 as the insulator of the magnetic tunnel junction and thereference layer FM3. N1 can also be an insulating layer so that FM1 andFM2 form a second magnetic tunnel junction. The reference layer FM3 canbe used to read the state of a device. The reference layer FM3 isseparated from the free magnetic layer FM2 by a non-magnetic layer N2.Various materials, as described above in greater detail, can be used tomake the various layers of the inverted layer stack 200. In addition,the layers can be of various different thicknesses.

FIG. 3 is an illustration of an inverted layer stack 300 in accordancewith an illustrative implementation. The thickness of the various layersare in nanometers (nm). In addition the FM1, FM2, FM3, N1, and N2 layersthat are related to the layers of those in FIG. 2 are shown. In theinverted stack 300, the magnetic tunnel junction layer 302 is at thebottom and the perpendicular polarizer 304 at the top. In someimplementations, the polarizer is deposited on top of the magnetictunnel junction, which is made up of the FM2, N2, and FM3 layers. In theinverted stack 300, the magnetic tunnel junction layer 302 are closer toa substrate or a semiconductor device (CMOS) wafer. The magnetic tunneljunction layer 302 are also smoother compared to the magnetic tunneljunction layers of a non-inverted layer stack with the polarizer at thebottom, e.g., FIG. 1. The increase of smoothness i.e., a reduction ofroughness, of the magnetic tunnel junction layer 302 reduces sharpcorners within the magnetic tunnel junction layer 302 and surroundinglayers. Specifically, the smoothness of a second non-magnetic layer N2(308) is increased when compared to a second non-magnetic layer of anon-inverted layer stack. Roughness within an insulating layer impactswhen and under what circumstances the magnetic tunnel breaks down. Theinverted stack 300 has a smoother non-magnetic layer 308 that improvesperformance of orthogonal spin transfer MRAM devices by increasing thebreakdown voltage and improving magnetic switching characteristics whencompared to orthogonal spin transfer MRAM devices that use anon-inverted layer stack. The inverted stack 300 also can reducevariations in device properties across a wafer. The Cu(N) layer is anoptional layer and in various implementations, this layer is notpresent. The Cu(N) layer forms an electrical contact to a device. Thiscontact can be part of the substrate, e.g., the CMOS drivers. The Cu(N)layer can also be made of different materials, such as, but not limitedto, Al, Ta, Cu.

FIGS. 6A-6D illustrate the difference in smoothness of the magnetictunnel junction layers between an inverted stack and a non-invertedlayer stack. FIGS. 6A and 6C are transmission electron microscope crosssections of a non-inverted layer stack. A second non-magnetic layer MgO602 can be seen at two different scales in FIGS. 6A and 6C. FIGS. 6B and6D are transmission electron microscope cross sections of an invertedlayer stack in accordance with an illustrative implementation. A secondnon-magnetic layer MgO 604 can be seen at two different scales in FIGS.6B and 6D. As can be seen in comparing FIGS. 6A and 6C with FIGS. 6B and6D, the second non-magnetic layer 604 is smoother than the secondnon-magnetic layer 602. The amplitude of the roughness of the MgO layerwas reduced from 2.9+/−2.7 nanometers (nm) in the non-inverted layerstack to 0.8+/−0.3 nm in the inverted layer stack. Here, the amplitudeis defined as the vertical distance between minima and maxima. Thewavelength of the roughness of the MgO layer was also reduced from33.1+/−11.0 nm in the non-inverted layer stack to 23.2+/−14.6 nm in theinverted stack. Here, the wavelength is defined as twice the horizontaldistance between the minima and maxima and maxima and minima,respectively. The reduced roughness results in a higher device breakdownvoltage that leads to a larger separation between the write voltage andthe breakdown voltage. This leads to a higher performance device thathas fewer device failures during operation.

Other inverted stacks can be produced with additional layers. FIG. 4 isan illustration of an inverted layer stack 400 with a syntheticantiferromagnet polarizer 404 in accordance with an illustrativeimplementation. The inverted layer stack 400 is similar to the invertedlayer stack 300 illustrated in FIG. 3. The difference is that theperpendicular polarizer 304 is incorporated into a syntheticantiferromagnet 404. A thin antiferromagnetic coupling layer 402 createsan antiparallel magnetic alignment of the two ferromagnetic layers 304and 405 in the synthetic antiferromagnet. This creates a syntheticantiferromagnet polarizer 404 that includes the perpendicular polarizer304. In the illustrated example the antiferromagnetic coupling layer iscomprised of Ruthenium. In this example, Ruthenium is one of thematerials in the synthetic antiferromagnet and is the layer that createsthe antiferromagnetic coupling between the Ni/Co and Pd/Co containinglayers. In other implementations, other synthetic antiferromagneticmaterials can be used, such as, but not limited to, chromium, copper,etc. The Cu(N) layer is an optional layer and in variousimplementations, this layer is not present.

The synthetic antiferromagnet polarizer 404 reduces the magneticinteractions between the perpendicular polarizer and the free magneticlayer FM2 in the inverted layer stack 400. The reduced magneticinteractions improves device performance, such as, but not limited to,more uniform rotation of the magnetization of the free layer duringswitching (e.g., writing data); reduction of the likelihood of undesiredthermally induced switching events (e.g., fluctuations that erase orcorrupt stored data).

FIG. 5 is an illustration of an inverted layer stack 500 with a pinnedsynthetic antiferromagnet polarizer 404 in accordance with anillustrative implementation. The inverted layer stack 500 is similar tothe inverted layer stack 400 illustrated in FIG. 4, but with theaddition of a layer of Iridium Manganese 502, an antiferromagnet. Inother implementations, other antiferromagnets are used. The addition ofthe antiferromagnet 502 pins the synthetic antiferromagnetic polarizer404 giving a perpendicular exchange bias. This makes the perpendicularpolarizer 304 magnetically harder and more stable against unwanteddemagnetization during usage of a device. This can lead to a longerdevice life and more repeatable device operation. The Cu(N) layer is anoptional layer and in various implementations, this layer is notpresent.

In addition to inverting the perpendicular polarizer, changing thematerials within the N1 layer can impact the properties of an invertedlayer stack. FIG. 7 is an illustration of an inverted magnetic tunneljunction 700 without a polarizer on top in accordance with anillustrative implementation. The Cu(N) layer is an optional layer and invarious implementations, this layer is not present. The invertedmagnetic tunnel junction 700 contains magnetic tunnel junction layer302, but there is no perpendicular polarizer. In an experiment, thetunnel magnetoresistance (TMR) was measured using the current in planetunneling technique (CIPT). A layer stack with Copper at the interfacewith the CoFeB free layer exhibited a TMR of 55% to 69% depending on thethickness of the MgO layer. In another experiment, the Copper layer wasremoved. The TMR increased significantly up to 157%. Table 1 belowsummarizes these findings. The thickness of the MgO layer was notoptimized and further increases may be achievable with an optimized MgOlayer, but such optimization is not material for operation of theinvention.

TABLE 1 With Cu Cap Without Cu Cap TMR %  55-69% 157% RA Ohm μm²2.5-14.4 6.18

While not limited to the following reason, Copper can induce itsface-centered cubic (fcc) crystalline structure into the CoFeB layerwith which it shares an interface. For an optimal TMR, a (body-centeredcubic) bcc texture of the CoFeB is favorable. The Copper layer canmagnetically decouple the polarizer and the magnetic tunnel junction. Inthese implementations, the Cu/CoFeB interfaces between the Copperinterlayer and the CoFeB free layer is the reason for the reducedelectric performance, e.g., smaller TMR. Using a bcc texture rather thanan fcc structure such as Copper, can increase the TMR of the stack. Inaddition, using a material that crystallizes at a higher temperaturethan the CoFeB favors the formation of bcc textured CoFeB and canincrease the TMR.

In one implementation, the Copper layer is replaced by a bccnon-magnetic layer. FIG. 8 is an illustration of an inverted layer stack800 in accordance with an illustrative implementation. The invertedlayer stack 800 is similar to the inverted stack 300 of FIG. 3 andcontains a non-magnetic layer N1. The materials of this N1 layer can bevarious materials. The Cu(N) layer is an optional layer and in variousimplementations, this layer is not present. FIG. 9 illustrates oneexample where the N1 layer is comprised of Copper. In this example, theinverted layer stack 800 is the same as the inverted stack 300 of FIG.3. The non-magnetic layer N1, however, can be made of other materials.As described above, replacing Copper, a fcc metal, with a bccnon-magnetic substance the TMR of the inverted layer stack 800 can beincreased. FIG. 10 illustrates this example. In FIG. 10, thenon-magnetic layer N1 is comprised of a bcc non-magnetic material 1002.The bcc non-magnetic material 1002 interfaces with the free magneticlayer FM2. In addition, the bcc non-magnetic material 1002 can supportthe growth of the underlying bcc free magnetic layer FM2, e.g., a CoFeBlayer. The bcc non-magnetic layer has a long spin diffusion length tomaintain the large perpendicular spin-polarization of the current afterpassing through the polarizer. Table 2 below summarizes some of thematerials that can be used as the bcc non-magnetic material 1002. Thethickness of the N1 layer when used with any of these materials can beless or approximately equal to the spin diffusion length of the materialused as the bcc non-magnetic material 1002.

TABLE 2 Atomic Crystal Magnetic Spin Diffusion Material Number StrucureOrder Length/nm V 23 bcc Paramagnetic >40 Cr 24 bcc Spin Density 4.5 at4 K Wave Antiferromagnet Nb 41 bcc Paramagnetic ~25 or 5.9 ± 0.3 Mo 42bcc Paramagnetic 8.6 ± 1.3 Ta 73 bcc Paramagnetic 2.7 ± 0.4

In another implementation, the non-magnetic layer N1 can be composed ofboth fcc and bcc materials. FIG. 11 is an illustration of an invertedlayer stack with a fcc non-magnetic layer 1004 and a bcc non-magneticlayer 1002 in accordance with an illustrative implementation. In thisimplementation, the bcc non-magnetic layer 1002 is adjacent to the freemagnetic layer FM1, e.g., CoFeB; and the fcc non-magnetic layer 1002 isadjacent to the polarizer. This ensures that the layers at theinterlayer/polarizer interface have the same fcc crystal structure andalso ensures that the layers at the interlayer/free layer interface havethe same bcc crystal structure. Various fcc and bcc materials can beused in this implementation. Table 3 summarizes some of the non-limitingcombinations of materials that can be used.

TABLE 3 Material Crystal Structure NM1/NM2 (thicknesses in nm) NM1/NM20.3 to 3Ta/7Cu bcc/fcc 0.3 to 3Ta/7Al bcc/fcc 0.3 to 3Cr/7Cu bcc/fcc 0.3to 3Cr/7Al bcc/fcc [1Cr/1Cu] × 5 bcc/fcc

FIG. 12 is a graph 1200 of current in plane tunneling measurements ofthe magnetoresistance of two layer stacks in accordance with anillustrative implementation. The graph 1200 illustrates themagnetoresistance of the inverted layer stack that does not have a Tainterlayer 1202. Such an inverted layer stack is shown in FIGS. 8 and 9.The magnetoresistance of an inverted layer stack that includes a Tainterlayer and a copper fcc non-magnetic layer 1204 is also shown. FIG.11 illustrates an example bcc non-magnetic interlayer. In testing, theMgO thickness was varied to produce layer stacks with different,systematically varying, resistance area (RA) products. This is shown inthe X-axis of the graph 1200. The magnetoresistance was increased forinverted layer stacks that included a bcc non-magnetic interlayer forall resistance area product stacks studied.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularinventions. Certain features described in this specification in thecontext of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresdescribed in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated in a single software product or packagedinto multiple software products.

Thus, particular implementations of the invention have been described.Other implementations are within the scope of the following claims. Insome cases as one of skill in the art would understand after readingthis disclosure, the actions recited in the claims can be performed in adifferent order and still achieve desirable results. In addition, theprocesses depicted in the accompanying figures do not necessarilyrequire the particular order shown, or sequential order, to achievedesirable results. In certain implementations, multitasking and parallelprocessing may be advantageous.

What is claimed is:
 1. A magnetic device comprising: a pinned magneticlayer having a first fixed magnetization vector with a first fixedmagnetization direction; a free magnetic layer comprising a firstbody-centered cubic material and having a variable magnetization vectorhaving at least a first stable state and a second stable state; a firstnon-magnetic layer spatially separating the pinned magnetic layer andthe free magnetic layer and including a second body-centered cubicmaterial that interfaces with the first body-centered cubic material; areference magnetic layer having a second fixed magnetization vector witha second fixed magnetization direction; and a second non-magnetic layerspatially separating the free magnetic layer and the reference magneticlayer, wherein a magnetic tunnel junction is formed by the free magneticlayer, the second non-magnetic layer, and the reference magnetic layer,wherein application of a current pulse, having a selected amplitude andduration, through the magnetic device switches the variablemagnetization vector, and wherein the magnetic tunnel junction isspatially located below the pinned magnetic layer.
 2. The magneticdevice of claim 1, wherein the second body-centered cubic materialincreases the magnetoresistance of the magnetic device.
 3. The magneticdevice of claim 1, wherein the second body-centered cubic material ofthe first non-magnetic layer is one of vanadium, chromium, niobium,molybdenum, and tantalum.
 4. The magnetic device of claim 1, wherein thefirst non-magnetic layer includes a face-centered cubic material thatinterfaces with a face-centered cubic material of the pinned magneticlayer.
 5. The magnetic device of claim 4, wherein the secondbody-centered cubic material of the first non-magnetic layer is one ofvanadium, chromium, niobium, molybdenum, and tantalum.
 6. The magneticdevice of claim 5, wherein the face-centered cubic material of the firstnon-magnetic layer is one of copper and aluminum.
 7. The magnetic deviceof claim 1, wherein the fixed magnetization vector is perpendicular tothe plane of the pinned magnetic layer.
 8. The magnetic device of claim1, further comprising a synthetic antiferromagnet layer, wherein thesynthetic antiferromagnet layer comprises the pinned magnetic layer. 9.The magnetic device of claim 8, wherein the synthetic antiferromagnetlayer reduces magnetic interactions between the pinned magnetic layerand the free magnetic layer.
 10. The magnetic device of claim 8, furthercomprising an antiferromagnet that pins the synthetic antiferromagnetlayer providing a perpendicular exchange bias.
 11. The magnetic deviceof claim 1, further comprising a second magnetic tunnel junctioncomprising the pinned magnetic layer and the free magnetic layer. 12.The magnetic device of claim 1, wherein the variable magnetizationvector represents a bit of information.
 13. A memory system comprising:a memory cell comprising: a pinned magnetic layer having a first fixedmagnetization vector with a first fixed magnetization direction; a freemagnetic layer comprising a first body-centered cubic material andhaving a variable magnetization vector having at least a first stablestate and a second stable state; a first non-magnetic layer spatiallyseparating the pinned magnetic layer and the free magnetic layer andincluding a second body-centered cubic material that interfaces with thefirst body-centered cubic material; a reference magnetic layer having asecond fixed magnetization vector with a second fixed magnetizationdirection; and a second non-magnetic layer spatially separating the freemagnetic layer and the reference magnetic layer, wherein a magnetictunnel junction is formed by the free magnetic layer, the secondnon-magnetic layer, and the reference magnetic layer, whereinapplication of a current pulse, having a selected amplitude andduration, through the magnetic device switches the variablemagnetization vector, and wherein the magnetic tunnel junction isspatially located below the pinned magnetic layer; and a current sourceconnected to the pinned magnetic layer and the reference magnetic layersuch that current passes through the memory cell.
 14. The memory systemof claim 13, wherein the second body-centered cubic material increasesthe magnetoresistance of the magnetic device.
 15. The memory system ofclaim 13, wherein the second body-centered cubic material of the firstnon-magnetic layer is one of vanadium, chromium, niobium, molybdenum,and tantalum.
 16. The memory system of claim 13, wherein the firstnon-magnetic layer includes a face-centered cubic material thatinterfaces with a face-centered cubic material of the pinned magneticlayer.
 17. The memory system of claim 16, wherein the secondbody-centered cubic material of the first non-magnetic layer is one ofvanadium, chromium, niobium, molybdenum, and tantalum.
 18. The memorysystem of claim 17, wherein the face-centered cubic material of thefirst non-magnetic layer is one of copper and aluminum.
 19. A method ofmaking a memory cell, comprising: forming a second non-magnetic layerspatially separating a free magnetic layer and a reference magneticlayer, wherein a magnetic tunnel junction is formed by the free magneticlayer, the second non-magnetic layer, and the reference magnetic layer,wherein application of a current pulse, having either positive ornegative polarity and a selected amplitude and duration, through themagnetic device switches a variable magnetization vector of the freemagnetic layer, and wherein the magnetic tunnel junction is spatiallylocated below a pinned magnetic layer; forming the reference magneticlayer having a second fixed magnetization vector with a second fixedmagnetization direction; forming a first non-magnetic layer spatiallyseparating the pinned magnetic layer and the free magnetic layer andcomprising a second body-centered cubic material that interfaces with afirst body-centered cubic material of the free magnetic layer; formingthe free magnetic layer comprising the first body-centered cubicmaterial and having a variable magnetization vector having at least afirst stable state and a second stable state; forming the pinnedmagnetic layer having a first fixed magnetization vector with a firstfixed magnetization direction;
 20. The method of claim 19, wherein thesecond body-centered cubic material increases the magnetoresistance ofthe magnetic device.